The present invention generally relates to preventing water condensation inside aircraft. Commercial aircraft may fly at altitudes where the outside air temperature is typically between 0 and −100 F. Although aircraft environmental control systems (ECS) provide warm and comfortable temperatures inside the cabin and cockpit, the temperatures on the inner surfaces of the aircraft skin may remain quite cold as heat is conducted through the skin to the outside air. The aircraft crew and passengers may be protected from these cold temperatures by interior cabin panels and insulation in the space between the interior panels and the aircraft skin, an area which may be referred to as the “aircraft crown”.
The aircraft crown may be vented to the cabin to maintain a low pressure differential between the aircraft crown and the cabin during changes in cabin pressure such as occur with changes in aircraft altitude. The low pressure differential may be needed to avoid damage to the interior cabin panels. However, this ventilation means that water vapor in the cabin air may enter the crown. A portion of this water vapor may condense on the cold inner surfaces of the aircraft skin. The condensed moisture may run down the inside surface of the skin, and may be collected in a trough and drained overboard. However, some of it may not be collected as it either drips off low angle surfaces or freezes along the way.
Condensation in the crown may cause a number of problems. The water or ice may accumulate, thus adding to the aircraft weight. The additional weight may negatively impact aircraft performance and increase fuel consumption. The water also may promote the formation of mold mildew which may damage the insulation or cause unpleasant odors in the cabin. And finally, the moisture can cause corrosion which may compromise the aircraft structure, electronic components and electrical connectors.
Existing zonal dryers may address this problem by using an enthalpy wheel and blower to dry a portion of the cabin air and distribute this dry air in the aircraft crown. An electric heater may be used to desorb moisture from the wheel. This added equipment may increase aircraft weight and cost, reduce reliability and require significant electric power to operate.
As can be seen, there is a need for an improved system for preventing water condensation inside aircraft.